The continuing objective of this project is to understand certain of the ways in which the behavioral actions of drugs depend on how particular behaviors are controlled by an individual's external environment. One focus is on behavior under control of aversive environmental stimuli, including procedures in which subjects (squirrel monkeys) actually work for access to normally noxious events. This behavior is compared with similar performances maintained by termination of noxious stimuli or by presentation of food. In addition to studying the contribution of characteristics of behavior such as its normal rate of occurrence, we are also studying the effects of an individuals's prior experience and of the total environmental context in which a behavior exists as determinants of the behavioral actions of drugs. Dose-effect relations for a variety of psychomotor stimulants, barbiturates, benzodiazepines, antidepressants, and antipsychotic drugs will be established under a variety of behavioral procedures. Since most psychoactive drugs are taken chronically, we are also studying the effects of these drugs given both acutely and on a longer-term daily basis. Through systematic study of the effects of a variety of psychoactive drugs under a broad range of past and present behavioral conditions, we hope to arrive at generalization that will prove useful in understanding and rationally predicting the clinical effects of drugs.